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At least 307 records · Page 17Linked to original sources

PubMed2003

Exercise training without ventricular remodeling in patients with moderate to severe left ventricular dysfunction early after acute myocardial infarction.

BACKGROUND: The purpose of this study was to determine whether or not patients with moderate to severe left ventricular (LV) dysfunction benefit from exercise training starting early after acute myocardial infarction (AMI) without deteriorating LV remodeling. METHODS: We investigated changes in exercise capacity and LV end-diastolic dimension (LVDd by two-dimensional echocardiography) before and after exercise training in 126 patients after AMI. Patients were divided into three groups according to LV ejection fraction (EF) at the beginning of exercise training: 74 patients with LVEF>/=45% (Group H), 35 patients with 35%</=LVEF<45% (Group M), and 17 patients with LVEF<35% (Group L). Exercise training was prescribed at a moderate intensity (50-60% of heart rate reserve or Karvonen's equation). Exercise capacity was assessed by peak work rate (WR) and peak oxygen uptake (VO(2)) by upright cardiopulmonary exercise test before and after 3 months of exercise training. LVDd was measured before and at 27+/-10 months of follow-up period. RESULTS: At the baseline, Group L had a significantly lower LVEF (H 55+/-7 vs. M 40+/-3 vs. L 30+/-3%, P<0.05), significantly greater LVDd (49+/-6 vs. 52+/-7 vs. 56+/-6 mm, P<0.05), and a higher incidence of anterior infarction (P<0.01) compared with Groups H and M, whereas there were no difference in age, sex, coronary risk factors, the incidence of multivessel disease, prior myocardial infarction, peak WR or peak VO(2) among the three groups. After 3 months of exercise training, exercise capacity increased significantly (all P<0.01) in all groups. The magnitudes of the increases in peak VO(2) (%Deltapeak VO(2): 18+/-20 vs. 15+/-19 vs. 18+/-17%, NS) and peak WR (%Deltapeak WR: 17+/-17 vs. 16+/-14 vs. 15+/-13%, NS) were similar among the three groups. In addition, there was no significant correlation between %Deltapeak VO(2) and baseline LVEF. No increase in LVDd was observed in any group at follow-up (H 48+/-5 to 49+/-4 mm vs. M 53+/-8 to 52+/-8 mm vs. L 57+/-5 to 57+/-7 mm, NS in each group). CONCLUSION: Patients with moderate to severe LV dysfunction benefit from exercise training starting early after AMI without deteriorating LV remodeling, with a similar magnitude of improvement in exercise capacity to that in patients with mild LV dysfunction.

Adult↗

PubMed2007

Effects of exercise training on heart rate and QT interval in healthy young individuals: are there gender differences?

AIMS: The aim of the present study was to assess the effects of exercise training on heart rate, QT interval, and on the relation between ventricular repolarization and heart rate in men and women. METHODS AND RESULTS: A 24 h Holter recording was obtained in 80 healthy subjects (40 males) who differed for the degree of physical activity. Trained individuals showed a lower heart rate and a higher heart rate variability than sedentary subjects, independent of the gender difference in basal heart rate. Mean 24 h QTc was similar in trained and non-trained men, while a significant difference was observed between trained and non-trained women. Exercise training reduced the QT/RR slope in both genders. This effect on the QT/RR relation was more marked in women; in fact, the gender difference in the ventricular repolarization duration at low heart rate observed in sedentary subjects was no longer present among trained individuals. CONCLUSION: The results of this study suggest that the cardiovascular response to exercise training may be different in men and women. Women may benefit more from interventions aimed to increase physical activity as a tool for prevention of cardiovascular morbidity and mortality.

Electrocardiography↗

PubMed1989

Exercise training in patients with chronic airways obstruction.

Some studies concerning the effects of specific and non-specific techniques of respiratory muscle training and new strategies in exercise training of both skeletal and respiratory muscles, are reviewed. Breathing and exercise training show some evidence of improved gas exchange. Breathing through an inspiratory resistance has some advantages but also disadvantages. This technique has caused immediate hypoxaemia and pulmonary arterial hypertension in one third of the subjects studied. High intensity exercise with correspondingly high levels of ventilation may induce improvements in ventilatory muscle function. Two new techniques are described: the "above anaerobic threshold 40 min constant exercise" and the "45 min square-wave endurance exercise test" (SWEET), simulating an interval-training session. The effects on the cardiorespiratory, metabolic, arterial blood gases and acid base balance responses, were measured in normal subjects and in patients with chronic airway obstruction (CAO). After training, the magnitude of ventilation (VE) reduction was correlated with the reduction in end-exercise lactate. In addition, maximal ventilation and maximal oxygen consumption (VO2max) can increase after training. Finally, an interesting hypothesis is proposed about the use of arm-training.

Aged↗

PubMed2000

Changes in ambient temperature at the onset of thermoregulatory responses in exercise-trained rats.

Spontaneous running in a wheel has emerged as a useful method of exercise in rodents. We investigated how exercise training with a running wheel affects ambient temperatures (T(a)) at the onset of thermoregulatory responses in rats. Female rats were allowed to run freely in the wheel for 6 months. Sedentary control rats did not exercise during the same period. After the exercise training period, they were loosely restrained and T(a) values at the onset of tail skin vasodilation and cold-induced thermogenesis were determined by raising or lowering T(a). Resting levels of core temperature and heat production of the exercise-trained rats were significantly higher than those of the controls. T(a) values at the onset of tail skin vasodilation and cold-induced thermogenesis of the exercise-trained rats were higher than those of the controls. The results suggest that, in rats, exercise training with a running wheel elevates ambient temperatures for heat loss and heat production, which may then contribute to maintaining the core temperature at a high level.

Adaptation, Physiological↗

PubMed2002

Exercise training alters length dependence of contractile properties in rat myocardium.

Myocardial function is enhanced by endurance exercise training, but the cellular mechanisms underlying this improved function remain unclear. Exercise training increases the sensitivity of rat cardiac myocytes to activation by Ca(2+), and this Ca(2+) sensitivity has been shown to be highly dependent on sarcomere length. We tested the hypothesis that exercise training increases this length dependence in cardiac myocytes. Female Sprague-Dawley rats were divided into sedentary control (C) and exercise-trained (T) groups. The T rats underwent 11 wk of progressive treadmill exercise. Heart weight increased by 14% in T compared with C rats, and plantaris muscle citrate synthase activity showed a 39% increase with training. Steady-state tension was determined in permeabilized myocytes by using solutions of various Ca(2+) concentration (pCa), and tension-pCa curves were generated at two different sarcomere lengths for each myocyte (1.9 and 2.3 microm). We found an increased sarcomere length dependence of both maximal tension and pCa(50) (the Ca(2+) concentration giving 50% of maximal tension) in T compared with C myocytes. The DeltapCa(50) between the long and short sarcomere length was 0.084 +/- 0.023 (mean +/- SD) in myocytes from C hearts compared with 0.132 +/- 0.014 in myocytes from T hearts (n = 50 myocytes per group). The Deltamaximal tension was 5.11 +/- 1.42 kN/m(2) in C myocytes and 9.01 +/- 1.28 in T myocytes. We conclude that exercise training increases the length dependence of maximal and submaximal tension in cardiac myocytes, and this change may underlie, at least in part, training-induced enhancement of myocardial function.

Actin Cytoskeleton↗

PubMed1997

Effect of prolonged exercise training without weight loss on high-density lipoprotein metabolism in overweight men.

This study examined the effect of exercise training without weight loss on high-density lipoprotein (HDL) metabolism in overweight men. We evaluated HDL metabolism using 125I-radiolabeled autologous HDL in 17 overweight men aged 40 +/- 7 years (mean +/- SD) before and after 1 year of exercise training. Subjects consumed defined diets in a metabolic kitchen during the metabolic studies. They performed endurance exercise under supervision for 1 hour four times weekly and maintained their pretraining body weight. Maximal oxygen uptake (VO2max) increased 27% (P < .001) with exercise training. HDL-cholesterol (HDL-C) and apolipoprotein (apo) A-I increased 10% and 9%, respectively (P < .001 for both), whereas triglycerides and apo B decreased 7% and 10%, respectively (P < .05). Postheparin lipoprotein lipase increased 11% (P = NS). Hepatic triglyceride lipase activity (HTGLA) decreased 12% (P < .05). The fractional catabolic rate (FCR) of HDL protein and of apo A-I decreased 5% and 7%, respectively (P < .05 for both). The synthetic rate of apo A-I increased 13% (P < .01). Increased HDL after exercise training is associated with both decreased HDL protein catabolism and increased HDL apo A-I synthesis. Weight loss is not required to increase HDL-C with exercise training in overweight men, but without weight loss, even prolonged exercise training produces only modest changes in HDL-C concentrations.

Adult↗

PubMed2005

Response of hepatic antioxidant system to exercise training in aging female rat.

This study was undertaken to investigate the effect of exercise training on aging in the hepatic oxidative status and antioxidant defense of female albino rat. Two age groups of 3 months and 12 months old Wistar strain female albino rats were given chronic exercise training for a period of 12 weeks. The antioxidant enzyme assays were carried out by the standard methods. Lower (P<0.01) activities of the antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR) by 21%, 44% and 63% respectively was observed in the older rats when compared to younger rats. Also, glutathione (GSH) levels were 42% lower (P<0.01) in older than younger animals. Exercise training to the 12 months aged rats significantly (P<0.01) elevated these antioxidant enzyme activities and GSH content, when compared to older control rats. These levels are almost equal to the values observed in the younger control rats. The levels of lipid peroxidation end product, malondialdehyde (MDA) the major indicator of oxidative stress, was found to increase with age (11%) and exercise training caused further elevation (28% of control). The present findings imply that the reactive oxygen species that are generated due to aging process were detoxified by the exercise induced antioxidant system in the liver tissue. These findings are also in agreement with similar changes in male animals, which clearly envisage no gender difference in the amelioration of the antioxidant enzyme system in older age due to exercise. In conclusion, it can be stated that twelve weeks treadmill exercise training has beneficial effect in improving antioxidant defense capacity by augmenting SOD, CAT and GR activities and GSH levels of older rats, thereby preventing oxidative damage to the liver tissue.

Aging↗

PubMed2006

Exercise training prevents Ca2+ dysregulation in coronary smooth muscle from diabetic dyslipidemic yucatan swine.

Aerobic exercise training is known to have profound cardioprotective effects in disease, yet cellular mechanisms remain largely undefined. We tested the hypothesis that increased sarcoplasmic reticulum Ca(2+) buffering and increased voltage-gated Ca(2+) channel density underlie coronary smooth muscle intracellular Ca(2+) (Ca(2+)(i)) dysregulation in diabetic dyslipidemia and that exercise training would prevent these increases. Yucatan swine were maintained in 1) control, 2) alloxan-induced hyperglycemic, 3) high fat/cholesterol fed, 4) hyperglycemic plus high fat/cholesterol fed (diabetic dyslipidemic), and 5) diabetic dyslipidemic plus exercise-trained (treadmill running) conditions. After 20 wk, the heart was removed and smooth muscle cells isolated from the right coronary artery. We utilized fura-2 imaging of Ca(2+)(i) levels to separate the functional role of the sarcoendoplasmic reticulum Ca(2+)-ATPase (SERCA) from the Na(+)-Ca(2+) exchanger and the plasmalemmal Ca(2+)-ATPase, and whole-cell patch clamp to examine voltage-gated Ca(2+) channel current density (i.e., Ca(2+) influx). Results indicated that diabetic dyslipidemia impaired plasmalemmal Ca(2+) efflux, increased basal Ca(2+)(i) levels, increased SERCA protein and sarcoplasmic reticulum Ca(2+)(i) buffering, and elicited an approximately 50% decrease in voltage-gated Ca(2+) channel current density. Exercise training concurrent with the diabetic dyslipidemic state restored plasmalemmal Ca(2+) efflux, SERCA protein, sarcoplasmic reticulum Ca(2+)(i) buffering, and voltage-gated Ca(2+) channel current density to control levels. Interestingly, basal Ca(2+)(i) levels were significantly lower in the exercise-trained group compared with control. Collectively, these results demonstrate a crucial role for exercise in the prevention of diabetic dyslipidemia-induced Ca(2+)(i) dysregulation.

Animals↗

PubMed2001

Intensive home-based exercise training in cardiac rehabilitation increases exercise capacity and heart rate variability.

BACKGROUND: Reduced heart rate variability (HRV) is a risk factor for cardiac death. Animal studies have shown increased HRV and reduced mortality after physical training. We evaluated the change in exercise capacity and HRV in cardiac rehabilitation patients, randomised to routine or home-based intensive training. The design was prospective, stratified randomisation with pre-specified subgroup analysis. METHODS: Maximal bicycle exercise test and 24-h Holter were performed 1 (baseline), 4 and 12 months after myocardial infarction (MI) or coronary artery by-pass surgery (CABG). Patients were randomised to physical training either two (N) or six (I) times per week for 3 months Sixty-two patients (43 MI and 19 CABG patients) were evaluated. RESULTS: Exercise capacity increased significantly more after 3 months of training in group I (mean (S.E.)); 29.0 (3.4) vs. 7.2 (2.6) watts, P<0.001). One year later the difference in exercise capacity remained (26.5 (3.3) vs. 11.8 (3.8) watts, P<0.001). Global HRV measurements SDNN and SDANN increased significantly more in group I after training (17.1 (5.6) vs. 1.7 (3.7) and 16.2 (4.9) vs. 2.8 (3.1) ms, P<0.05) and 1 year later the differences were still significant. Subgroup analysis showed more pronounced HRV response in CABG than MI patients. CONCLUSION: Intensive exercise training in cardiac rehabilitation increases exercise capacity and global HRV, which could be of prognostic significance.

Coronary Artery Bypass↗

PubMed2003

Adaptation of pulmonary oxygen consumption slow component following 6 weeks of exercise training above and below the lactate threshold in untrained men.

STUDY OBJECTIVES: To examine the effects of 6 weeks of exercise training above or below the lactate threshold (LT) on the slow component (SC) of pulmonary oxygen consumption (.VO(2)). DESIGN: Randomized controlled trial. SETTING: University human performance laboratory. PARTICIPANTS: Apparently healthy, untrained men (n = 18). INTERVENTIONS: Subjects were randomized to one of three groups: high-intensity exercise training (HI) [above the LT], moderate-intensity exercise training (MOD) [below the LT], or no exercise training (CON). Exercise groups performed cycle ergometry 4 d/wk for 6 weeks. Total work throughout training was constant between groups. MEASUREMENTS AND RESULTS: Maximal cycle ergometry was performed at baseline and after training to assess power output at the LT (WLT), .VO(2) at the LT (.VO(2)LT), and peak .VO(2) (.VO(2)PK). High-intensity, constant-load cycling was performed at baseline and weeks 1, 2, 4, and 6 to assess SC adaptations. WLT, .VO(2)LT, and .VO(2)PK increased after 6 weeks in both exercise groups compared to the CON group (p < 0.05), although there were no differences between the training groups. SC of .VO(2) decreased 44% in the HI group following 1 week of exercise training vs MOD (20%, p < 0.05) and CON (12%, p < 0.01) groups. The SC attenuation was more prominent at all time points in the HI group compared to the MOD group. Total SC attenuation over the 6-week training period did not differ between the HI (71%) and MOD (57%) groups. CONCLUSIONS: Training at HI or MOD produced similar improvements in the LT, .VO(2), and power output at peak exertion when total work output was held constant. Attenuation of the SC with training above and below the LT were similar, although above-LT training promoted faster SC adaptations.

Adult↗

PubMed1997

Exercise training improves functional recovery and motor nerve conduction velocity after sciatic nerve crush lesion in the rat.

OBJECTIVE: To observe the effects of exercise training on recuperation of sensorimotor function in the early phase of regeneration, and to monitor the long-term effects of exercise on electrophysiological aspects of the regenerating nerve. DESIGN: After sciatic nerve crush in 20 male Wistar rats, one random selected group was subjected to 24 days of exercise training, whereas the other group served as sedentary controls. INTERVENTIONS: Exercise training was induced for 24 days, starting the first postoperation day, by placing bottles of water at such a height that the exercising rats had to maximally erect on both hindpaws to drink. MAIN OUTCOME MEASURES: Recovery of motor and sensory function in the early phase was monitored by analysis of the free walking pattern and the foot reflex withdrawal test, respectively. Electrophysiological measurements on postoperation days 50, 75, 100, 125, and 150 were used to evaluate the late phase of recovery of nerve conduction velocity. RESULTS: During the early phase of the recovery period, exercise training enhanced functional recovery. The motor nerve conduction velocity (MNCV), as measured in the late phase of recovery, was significantly better in the trained group than in the control group (p < .01). CONCLUSIONS: We conclude that exercise training enhances the return of sensomotoric function in the early phase of recovery from peripheral nerve lesion. Furthermore, these results suggest that the beneficial effects of 24 days of exercise training after crush persist in the late phase of peripheral nerve recovery.

Animals↗

PubMed1991

Effect of beta-blockers on exercise physiology: implications for exercise training.

We conducted a series of studies aimed at investigating the effect of beta-blockers on exercise physiology. On the basis of these and other existing studies, it is possible to draw the following conclusions and to make the following tentative recommendations for patients engaged in exercise training who receive beta-blocker therapy: i) CAD patients treated with beta-blockers are capable of deriving the expected enhancement of cardiorespiratory fitness during training, irrespective of the type of drug used; ii) beta1-selective blockers are preferable to nonselective agents for hypertensive patients engaged in exercise training; iii) because beta1-selective blockers impair exercise tolerance in some hypertensive patients, physicians should look out for this adverse reaction and, if present, consider alternative antihypertensive therapy; iv) intrinsic sympathomimetic activity confers no advantage during exercise training; v) exercise intensity prescription for patients receiving beta-blockers should be in accordance with traditional guidelines and based on results of individualized exercise testing performed on medication; vi) exercise training is desirable during beta-blocker therapy in that it appears to offset adverse alterations in lipoprotein metabolism; and vii) nonselective beta-blockers may increase predisposition to exertional hyperthermia, and patients must therefore be encouraged to adhere strictly to accepted guidelines for heat injury prevention.

Adrenergic beta-Antagonists↗

PubMed1996

Comparative effects of exercise training on transcription of antioxidant enzyme and the activity in old rat heart.

An increase in antioxidant enzyme activity after acute exercise and exercise training have been reported by many investigators including our laboratory. This study was undertaken in order to determine whether an increase in activity of superoxide dismutase (MnSOD and CuZnSOD), catalase (CAT) and glutathione peroxidase (GSH-Px) during exercise training was associated with the increased levels of respective mRNAs. Male Fisher-344 rats (age 77 weeks) were given exercise training for 9 weeks on the treadmill. Enzyme activity and mRNA's were measured in the heart tissue 23 hr after stopping exercise training. The heart tissues of exercised and sedentary control rats were used to isolate mRNAs encoding MnSOD, CuZnSOD, CAT and GSH-Px by northern blotting experiments. The intensities of mRNA bands were measured by densitometric scanning of the autoradiograms. Northern blot for tubulin was used to normalize the respective intensities. Compared to sedentary controls, the level of mRNAs of enzymes MnSOD, CAT and GSH-Px were found to increase by 126 +/- 5, 133 +/- 6, and 138 +/- 5 percent of sedentary control (mean +/- SEM) respectively, due to exercise training. Corresponding values for these enzyme activity were 153 +/- 19%, 255 +/- 7%, 133 +/- 2% of sedentary control. These results suggest that post-translational modification of these enzyme activity increased in response to exercise training more than increased transcription in aged rats.

Animals↗

PubMed2001

Exercise training improves insulin-mediated capillary recruitment in association with glucose uptake in rat hindlimb.

Exercise training is considered to be beneficial in the treatment and prevention of insulin insensitivity, and much of the effect occurs in muscle. We have recently shown that capillary recruitment by insulin in vivo is associated with and may facilitate insulin action to increase muscle glucose uptake. In the present study, we examined the effect of 14 days of voluntary exercise training on euglycemic-hyperinsulinemic clamped (10 mU. min(-1). kg(-1) for 2 h), anesthetized rats. Whole-body glucose infusion rate (GIR), hindleg glucose uptake, femoral blood flow (FBF), vascular resistance, and capillary recruitment, as measured by metabolism of infused 1-methylxanthine (1-MX), were assessed. In sedentary animals, insulin caused a significant (P < 0.05) increase in FBF (1.6-fold) and capillary recruitment (1.7-fold) but a significant decrease in vascular resistance. In addition, hindleg glucose uptake was increased (4.3-fold). Exercise training increased insulin-mediated GIR (24%), hindleg glucose uptake (93%), and capillary recruitment (62%) relative to sedentary animals. Neither capillary density nor total xanthine-oxidase activity in skeletal muscle were increased as a result of the training regimen used. We concluded that exercise training improves insulin-mediated increases in capillary recruitment in combination with augmented muscle glucose uptake. Increased insulin-mediated glucose uptake may in part result from the improved hemodynamic control attributable to exercise training.

Animals↗

PubMed2004

Effect of exercise training on interdialytic ambulatory and treatment-related blood pressure in hemodialysis patients.

BACKGROUND: Exercise training improves blood pressure (BP) in the general population, but prior studies in hemodialysis (HD) patients only used pill counts or treatment-related BPs. We evaluated the effect of 3 to 6 months of intradialytic exercise training on ambulatory blood pressure (ABP) and treatment-related pre- and postdialysis BP. PATIENTS AND METHODS: Nineteen chronic HD patients trained with an exercise bicycle for 30 to 60 min in the first 1 to 2 hr of each of thrice weekly HD. Interdialytic 44-hr ABP was performed a week before training began and repeated at 3 and 6 months. Pre- and post-HD systolic and diastolic BP and pre- and post-HD weight were recorded for 2 months prior to training, throughout the training, and, if available, for the 2 months after training ended. BP medications were recorded throughout. Body composition by bioimpedance, and norepinephrine and epinephrine levels by RIA were done at 0, 3, and 6 months. RESULTS: Thirteen subjects who completed at least 3 months of training exercised 90% of HD sessions for 56 min +/- 23 SD each. Systolic and diastolic 44-hr interdialytic ABP fell during training (systolic 138.4 mmHg +/- 19.6 vs. 125.7 mmHg +/- 20.0 vs. 125.9 mmHg +/- 22.9; diastolic 83.2 mmHg +/- 10.2 vs. 74.7 mmHg +/- 9.0 vs. 73.9 mmHg +/- 11.8 at 0, 3, and 6 months; p < .05 ANOVA). Norepinephrine and epinephrine levels did not independently predict systolic BP. Pre-HD systolic BP was stable during the pretraining period, fell significantly during the training period (p < .03), and returned toward preexercise levels during the posttraining period (p < .001). Pre- or postweight, erythropoietin dose, total body water, and number of BP meds were unchanged. CONCLUSION: Exercise training during HD significantly improves both interdialytic ABP and treatment-related BP.

Adult↗

PubMed1998

The influence of moderate and chronic exercise training on the pharmacokinetics of procainamide and N-acetylprocainamide.

The effect of moderate and prolonged exercise on the disposition and metabolism of drugs has not been extensively examined. The present study examined the effect of exercise training on the pharmacokinetics of procainamide and its active metabolite, N-acetylprocainamide. Male Sprague Dawley rats were randomly assigned to three testing groups: (1) sedentary, (2) 4 weeks of exercise training and (3) 8 weeks of exercise training. Treadmill speed and exercise duration were gradually increased, reaching a final rate of 24 m min-1 for an hour by the end of the 4-week or 8-week period. Sedentary and exercise trained rats received a single i.p. dose of procainamide (100 mg kg-1). Serial blood samples were collected over a 10 h period and plasma samples were analysed by an UV-HPLC method. Noncompartmental analysis was performed to estimate the pharmacokinetic parameters. The t1/2 of procainamide was significantly (p < 0.05) higher in the 8 week exercise group (331 min) as compared to the sedentary group (77 min). In addition, there was a significant reduction in the amount of N-acetylprocainamide formed after 8 weeks of exercise (AUCNAPA = 739 ng mL-1 min-1). Results of this study suggest that prolonged exercise (8 weeks of training) alters the pharmacokinetics of procainamide by modifying the amount of active metabolite formed.

Acecainide↗

PubMed2000

Chronic exercise training does not alter pulmonary vasorelaxation in normal pigs.

Exercise training increases acetylcholine-induced pulmonary vasorelaxation in pigs with coronary occlusion. The present study tested the hypothesis that chronic exercise training enhances endothelium-mediated vasorelaxation in pulmonary arteries from normal pigs. Yucatan miniswine exercised for 16 wk on a treadmill (Ex); control pigs (Sed) remained in pens. Pulmonary artery rings (2- to 3-mm OD) were studied using standard isometric techniques. Contractile responses to 80 mM KCl and norepinephrine (NE) were determined. Vessels were constricted with levels of NE that resulted in half-maximal contraction to examine endothelium-dependent relaxation to ACh and endothelium-independent relaxation to sodium nitroprusside in the presence and absence of nitric oxide synthase inhibition, cyclooxygenase inhibition, and endothelial denudation. Arteries from Ex pigs developed increased contraction to 80 mM KCl, but the response to NE did not differ between groups. Endothelium-dependent and endothelium-independent responses did not differ between Sed and Ex in the presence or absence of pharmacological inhibitors or denudation. We conclude that chronic exercise training does not alter endothelium-dependent or endothelium-independent vasorelaxation responses of pulmonary arteries from normal pigs.

Acetylcholine↗

PubMed1986

Age-related differences in effect of exercise training on cardiac muscle function in rats.

To test the hypothesis that age may alter the effect of exercise training on myocardial function, we trained young adult (4-5 mo at study initiation) and old (21 mo at initiation) male Fischer 344 rats to run on a rodent treadmill 5 days/wk for 4.5 mo and compared their myocardial function with that of age-matched sedentary controls. Right ventricular papillary muscles were isolated from the young adult and aged animals and stimulated at the length at which developed isometric tension was maximal to contract isometrically at 12/min, bathed in oxygenated modified Krebs solution, and studied at 28 degrees, 32 degrees, 35 degrees, and 38 degrees C. In the absence of cardiac hypertrophy, exercise training significantly reversed the age-related prolongation of isometric contraction duration in the senescent rat (P less than 0.001). However, exercise training prolonged contraction duration in the young adult rat (P less than 0.05). The relaxation phase was more sensitive than the contraction phase to changes in temperature, especially in the aged rat (P less than 0.02). The ratio of developed tension to time-to-peak tension of the isometric twitch was not affected by exercise training. Because exercise training affects cardiac function in opposite directions from young adulthood to senescence, caution is advised in extrapolating results from exercise studies in young adult rats to populations of older animals.

Aging↗